Nucleophilic Attack at Pentaarsaferrocene [Cp*Fe(η5 -As5 )]-The Way to Larger Polyarsenide Ligands

Abstract

By the reaction of [Cp*Fe(η⁵ -As₅ )] (I) (Cp*=C₅ Me₅ ) with main group nucleophiles, unique functionalized products with η⁴ -coordinated polyarsenide (As_n ) units (n=5, 6, 20) are obtained. With carbon-based nucleophiles such as MeLi or KBn (Bn=CH₂ Ph), the anionic organo-substituted polyarsenide complexes, [Li(2.2.2-cryptand)][Cp*Fe(η⁴ -As₅ Me)] (1 a) and [K(2.2.2-cryptand)][Cp*Fe{η⁴ -As₅ (CH₂ Ph)}] (1 b), are accessible. The use of KAsPh₂ leads to a selective and controlled extension of the As₅ unit and the formation of the monoanionic compound [K(2.2.2-cryptand][Cp*Fe(η⁴ -As₆ Ph₂ )] (2). When I is reacted with [M]As(SiMe₃ )₂ (M=Li ⋅ THF; K), the formation of the largest known anionic polyarsenide unit in [M'(2.2.2-cryptand)]₂ [(Cp*Fe)₄ {μ₅ -η⁴ :η⁴ :η³ :η³ :η¹ :η¹ -As₂₀ }] (3) occurred (M'=Li (3 a), K (3 b)).

Keywords: Arsenic; Functionalization; Iron; Nucleophiles; Polyarsenide Units.